types(3) - NetBSD Manual Pages

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TYPES(3)                NetBSD Library Functions Manual               TYPES(3)


NAME

     types -- standard system data types


SYNOPSIS

     #include <sys/types.h>


DESCRIPTION

     The <sys/types.h> header contains the common data types used in the sys-
     tem.  Although these are meant to be used within the kernel, most of the
     system data types are accessible also to user code.  A companion header
     <sys/param.h>, typically used in the kernel, includes <sys/types.h> and
     provides additional types as well as other facilities (see param(3)).

   Standard Types
     The following standards-compliant system data types are defined:

           Type            Typical use                       Example
           blkcnt_t        file block counts                 stat(2)
           blksize_t       block sizes                       stat(2)
           clock_t         system clock ticks                clock(3)
           clockid_t       clock IDs                         clock_settime(2)
           dev_t           device IDs                        devname(3)
           fsblkcnt_t      file system block counts          -
           fsfilcnt_t      file system file counts           -
           gid_t           group IDs                         getgid(2)
           id_t            general identifier                pset(3)
           ino_t           file serial numbers               fs(5)
           key_t           interprocess communication        ftok(3)
           mode_t          file attributes                   stat(2)
           nlink_t         link counts                       stat(2)
           off_t           file sizes                        fseek(3)
           pid_t           process and process group IDs     getpid(2)
           size_t          size of objects                   stddef(3)
           ssize_t         count of bytes                    write(2)
           suseconds_t     microseconds                      gettimeofday(2)
           time_t          time in seconds                   time(3)
           timer_t         timer IDs                         timer_create(2)
           uid_t           user IDs                          setuid(2)
           useconds_t      time in microseconds              usleep(3)

     In addition, when included in user applications, <sys/types.h> includes
     <pthread.h>, and thus it defines also the types used in the POSIX Threads
     Library, pthread(3).

     Each described type may vary across machines and operating systems.  Only
     the following properties are guaranteed by the IEEE Std 1003.1-2001
     (``POSIX.1'') standard:

           1.   The type ssize_t is capable of storing integer values at least
                in the range [-1, SSIZE_MAX].

           2.   The type useconds_t is an unsigned integer capable of storing
                values at least in the range [0, 1000000].

           3.   The type suseconds_t is a signed integer capable of storing
                values at least in the range [-1, 1000000].

           4.   The time_t and clock_t types are either integers or real-
                floating types.

           5.   The following types are integers: gid_t, id_t, mode_t,
                nlink_t, and uid_t.

           6.   The following types are signed integers: blkcnt_t, blksize_t,
                off_t, pid_t, and ssize_t.

           7.   The following types are unsigned integers: fsblkcnt_t,
                fsfilcnt_t, ino_t, and size_t.

   NetBSD-specific Types
     In addition to the standard types, <sys/types.h> defines some data types
     specific to NetBSD.  These are mostly used in the kernel.  A portable
     implementation should not rely on these types to be available in other
     systems.  Examples include:

           Type            Typical use                Example
           cpuid_t         CPU IDs                    cpuset(3)
           daddr_t         disk address               buffercache(9)
           devmajor_t      major device number        getdevmajor(3)
           lwp_t           typedef of struct lwp      kthread(9)
           u_quad_t        synonym for uint64_t       strtouq(3)

     It can be noted that the standard ``C99 types'' described in stdint(3)
     are preferred to the older fixed size integer types prefixed with an
     ``u_'' (in other words, uint32_t should be used instead of u_int32_t).


SEE ALSO

     param(3), stdbool(3), stddef(3), stdint(3), stdlib(3), unistd(3)


STANDARDS

     The <sys/types.h> header conforms to IEEE Std 1003.1-2001 (``POSIX.1'')
     with respect to the described standard types.


HISTORY

     The <sys/types.h> header first appeared in Version 7 AT&T UNIX.  In the
     current form the header appeared in NetBSD 0.9.

NetBSD 10.1                     April 10, 2011                     NetBSD 10.1